Heat developable light-sensitive photographic material



United States Patent Ofilice 3,348,945 Patented Oct. 24, 1957 3,348,945 IEAT DEVELOPABLE LIGHT-SENSITIVE PHOTOGRAPI-HC MATERIAL Helmut Miider and Hans Ulrich, Leverkusen, Walter Piischel, Koeln-Stammheim, and Anita von Kiinig, Leverknsen, Germany, assignors to Agfa Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Feb. 4, 1964, Ser. No. 342,528 Claims priority, application Germany, Feb. 18, 1963,

A 42,356, Patent 1,174,159 7 Claims. (Cl. 96-29) ABSTRACT OF THE DISCLOSURE Heat development of exposed silver halide emulsions is accomplished with the usual moisture-or alkali-providing additives reduced in concentration or entirely eliminated by incorporating a compound of the formula in which R represents a hydrogen atom, or an alkyl or aryl group, such as a phenyl or naphthyl group, which groups may be substituted, R an optionally substituted aryl radical or a heterocyclic radical, R and R together are moreover able to represent the ring members necessary for forming a ring system, preferably a carbocylic ring system, R represents a hydrogen atom or an optionally substituted alkyl or aryl radical, and R represents an electron-attracting group, e.g. NO o-r CEN. Heat development of the foregoing emulsions can be used either in a conventional or in a diffusion transfer operation in which excess developer is transferred.

The invention relates to a photographic material comprising a light sensitive silver halide emulsion layer, which material contains a silver halide developer substance and is developable by the application of heat without the use of a liquid developing solution.

The heat development of imagewise exposed silver halide emulsion layers is known in principle from German patent specification No. 888,045. In order to increase the sensitivity of heat-developable photographic materials, substances which contain water in loosely combined form, e.g. inorganic salts forming definite hydrates in solid phase, are added to the emulsion layers. The Water liberated by the action of heat probably leads to an increase in the developer activity in the layer. Substances can also be added to the layers, which substances are decomposed on being heated in the presence of moisture to form substances having an alkali reaction; e.g. sodium trichloracetate can be used and this dissociates into sodium bicarbonate and chloroform.

A developer-containing, heat developable photographic material is known from British specification No. 930,572, which contains a 3-pyrazolidone silver halide developing agent and an alkaline substance for accelerating development of a latent image.

However, the use of relatively large quantities of alkaline substances with heat-developable photographic materials leads to a relatively strong fogging. The liability to fogging is certainly reduced with smaller quantities of alkali, but the photographic material has a lower sensitivity and the developed images do not have sufficient density. Furthermore, with addition of substances which form defined hydrates in solid form, e.g. sodium acetate, photographic silver halide emulsions have a tendency to tackiness after casting, and this renders the making-up and packing difficult. Developer-containing materials which are for example produced with sodium acetate are also not suitable for storage.

The invention has for its object to produce a heat developable photographic material which does not have the aforementioned disadvantages.

According to the present invention, there is provided a heat-developable photographic material comprising a support bearing a light sensitive silver halide emulsion layer, which material contains a silver halide developer substance and a compound of the following general formula R1 R3 l l\ R, OH H R in which R represents a hydrogen atom, or an alkyl or aryl group, such as a phenyl or naphthyl group, which groups may be substituted,

R an optionally substituted aryl radical or a heterocyclic radical,

R and R together are moreover able to represent the ring members necessary for forming a ring system, preferably a carbocyclic ring system,

R represents a hydrogen atom or an optionally substituted alkyl or aryl radical,

R represents an electron-attracting group, e.g. -NO or --CEN.

The preferred compounds are B-nitroethanols which are substituted in u-position by a phenyl radical or by a phenyl radical which is substituted by an alkyl group having preferably 1-5 carbon atoms, an alkoXy group having 1-5 C-atoms in the alkyl radical and/ or a halogen atom, such as chlorine and bromine.

By introducing such compounds into photographic silver halide emulsion layers or adjacent layers which have an incorporated developer substance, images with good speed and density gradation are obtained after exposure to light and heat development. Simultaneously, the stability in storage of such materials is improved.

By adding the compounds according to the invention, alkalis or compounds which split off alkalis or water under the action of heat become substantially superfluous. In individual cases, such compounds can of course be added, but the quantity necessary is so small that the photographic properties of the material and its stability in storage are notimpairecl. Suitable compounds are for example:

a-Phenyl-B-nitroethanol a-4-methoxyphenyl-fi-nitroethan ol a-Z-furyl-fi-nitroethanol l-nitromethybcyclohexanol-i The compounds to 1 to 5 are prepared by the process which is described in Zeitschrift fiir Naturforshung, Year 1952, vol. 712, pages 344*352, by reacting aromatic or heterocyclic aldehydes with nitromethane in the presence of sodium.methylate in alcoholic solution.

Compound 6 is prepared in analogous manner by reacting cyclohexanone with nitromethane. A distillation of the crude product obtained after the working up is not possible because of decomposition.

Compound 7 is prepared by the following method: 60 g. of 4-methylbenzaldehyde and 58.5 g. of benzyl cyanide are dissolved in 300 ml. of absolute alcohol. At a temperature of 5 to 8 C., a sodium methylate solution prepared from 11.5 g. of sodium and 300 ml. of absolute methanol is introduced dropwise while stirring. Heating then takes place for 2 /2 hours to 50 C. On cooling, an orange-red precipitate is formed, and after this has been suction-filtered and washed with methanol, it is introduced into a mixture of 140 g. of ice, 280 ml. of Water.

and 80 g. of glacial acetic acid. The White crystal mass is suction-filtered, washed with cold water and dried. M.P. 51-52 C.

Compounds 8 to 11 are obtainable in corresponding manners.

For the preparation of a heat-developable, photographic material, a silver halide emulsion containing 0.050.5 g. mole of silver halide per liter has added thereto a developer substance, e.g. a 3-pyrazolidone, in quantities of 5-20 g. per liter and one of the condensation products according to the invention in quantities of about 10-50 g., advantageously 20-40 g. per liter, and the mixture is cast on to a suitable support, e.g. a paper or film support.

These materials may usually contain 1-10 g. of said con-.

densation products per square meter. In order further to activate the developer, it is also. possible to introduce into the emulsion an inorganic salt which contains water of crystallisation or which has an alkaline reaction. e.g. sodium acetate, sodium carbonate or sodium sulphate.

These additions may also be incorporated wholly or partially into auxiliary colloid layers underlying or overlying the emulsion layer, such as gelatin layers.

The compounds used according to the invention may be dissolved in highest possible concentration in a suitable solvent such as methanol, ethanol, dimethylformamide and the like and added in this form to the casting solution. The compounds can be present in the emulsion layers or auxiliary layers in a dissolved or finely divided form.

After imagewise exposure, the material is heated for 1 to 3 seconds to temperatures of approximately 70-160 C., advantageously -150 C., the material being thus developed. The fixing is then eifected in the usual manner with organic or inorganic fixing agents, e.g. sodium thiosulphate or mercapto compounds.

Such quickly developable photographic materials are of importance in all cases where a photographically recorded operation is tobe quickly evaluated, e.g. with recording papers.

Silver chloride or silver bromide or mixtures thereof, possibly with a small addition of silver iodide, are suitable as light-sensitive silver salts. If necessary, the layers can also be optically sensitised, for example, when processes registered on a cathode ray oscillograph are to be photographically recorded.

The degree of hardening of the layers is of subordinate importance as regards the efiicacy of the layers according to the invention, but it must be adapted to the actual purpose for which the layers are used.

To be considered as binding agents for the photographic layers are all known layer-forming colloids, more especially gelatin, which can be wholly or partially replaced.

by other layer-forming substances, e.g. cellulose derivatives such as carboxymethyl cellulose, methyl hydroxyethyl cellulose, polyvinylalcohol, polyvinyl acetal, polyvinyl acetate, partially hydrolysed polyvinyl acetates, alginic acid derivatives such as alginates, alginic acid propylene glycol ester, polyvinyl pyrrolidone, zein and other natural or synthetic substances. The additives usual in the emulsion art can be used in the silver halide emulsion, for example, antifogging agents, such as benztriazolc, 1-phenyl-S-mercaptotetrazole, 4-hydroxy-6-methyl- 1,2,3a,7-tetrazaindene and others.

Developer substances of the pyrazolidone series are excellently suitable for the light-sensitive material according to the present invention. Examples of these are the following compounds:

1-phenyl-3-pyrazolidone 1-m-tolyl-3-pyrazolidone 1-p-tolyl-3-pyrazolidone l-phenyl-4-methyl-3-pyrazolidone 1-phenyl-5-methyl-3-pyrazolidone l,4-dimethyl-3-pyrazolidone 4-methyl-3-pyrazolidone 4,4-dimethyl-3-pyrazolidone 1-phenyl-4,4-dimethyl-3-pyrazolidone 1- (4-bromophenyl -3 -pyrazolidone The emulsion layer can be cast on to any suitable layer support which is durable at the temperatures of the heat development, e.g. paper, baryta-coated paper, filmforming synthetic polymers such as polycarbonate, more especially based on bis-hydroxyarylalkanes or polyesters based on terephthalic acid and ethylene glycol, as well as cellulose esters, fabrics or metal foils.

Negative materials with a content of the substances according to the invention can also be used for transfer processes, more especially with developer transfer processes. With processes of this type, the developer not used in the unexposed areas of the negative layer is transferred by heat into a transfer layer in contact therewith and are utilised therein for the production of coloured images.

In this connection, reference is to be made for example to the process of copending application S.N. 303,685, filed Aug. 21, 1963. The negative material used in the process described therein contains considerable quantities of sodium acetate, which can be wholly or partially replaced by the compounds according to the invention. Thereby, the storability is considerably improved.

EXAMPLE 1 To 1 liter of a gelatine silver chloride emulsion containing 0.3 mole of silver chloride per liter there are added:

20 mg. of 1-phenyl-5-mercaptotetrazole (1% in alcohol) 20 ml. of saponin solution (5% in water) 3 ml. of formalin (30% in water) g. of 1-phenyl-3-pyrazolidone and g. of compound 1 (dissolved in a little alcohol).

The casting solution thus prepared is applied in the usual way to baryta-coated paper and dried.

After exposure to form an image, the material is heated to about 120 C. for 2 seconds in close contact with a heated metal plate or a pair of heated rollers. A blackishbrown image is obtained, which can be stabilised in the usual way with an acid fixing bath.

EXAMPLE 2 A photographic material as described in Example 1 is prepared by using 20 g. of compound 2 instead of compound 1. After the exposure to form a latent image, it is heated for, 2 /2 seconds to 100 C., a brownish-black image being formed. It is fixed in the usual way with an acid fixing bath.

EXAMPLE 3 To 1 liter of a silver chloride emulsion there are added:

30 mg. of 1-phenyl-5-mercaptotetrazole (1% in alcohol) 20 ml. of saponin solution (5% in water) 10 g. of l-phenyl-3-pyrazolidone 30 g. of compound 7 (in a little alcohol) and 3 ml of formalin (30% in water).

The emulsion is cast on to baryta-coated paper. After exposure, it is heated for 2 seconds to 120 C. A violet black image is obtained.

EXAMPLE 4 An emulsion is prepared as described in Example 3, but 40 g. of the compound 6 are used instead of compound 7. After development, a brownish-black image is obtained.

EXAMPLE 5 To 1 liter of a silver chloride emulsion there are added:

20 mg. of 1-phenyl-S-mercaptotetrazole (1% in alcohol) 20 ml. of saponin solution (5% in water) 3 ml. of formalin (30% in water) 12 g. of 1-phenyl-3-pyrazolidone 20 g. of compound 2 (in a little alcohol) and 5 g. of sodium acetate.

After being applied in the usual way to a suitable layer support (paper or film), the film obtained is exposed to form an image and heated for 2 seconds to 120 C. A black image is obtained. The same material, but without the compound 2, merely gives -a brown image of weaker density after the dry development.

. e EXAMPLE 6 This example describes the use of the compounds according to the invention in a transfer process.

Negative material To 1 liter of a silver chloride emulsion there are added:

0.5 g. of benztriazole (5% in alcohol) 200 cc. of a 15% hydrosol of silicic acid 20 g. of crystalline sodium acetate 50 g. of compound 7 and 7.5 g. of 1-phenyl-3-pyrazolidone.

The pH value is adjusted with sulphuric acid to 4.9. The emulsion is applied in known manner to a layer support, e.g. paper, and dried.

Positive material The positive (transfer) material is prepared as follows: 1 gram of a cobalt leucophthalocyanine, such as Phthalogen'blau 1B of Far-benfabriken Bayer A.G., dissolved in 30 ml. of a polyethylene glycol having an average molecular weight of about 400, 2 ml. of lactic acid, 3 g. of tartaric acid and 5 ml. of a 30% aqueous solution of saponine are added to 1 liter of a 0.7% aqueous solution of a gallactomannan, for example Guar CSAA (trade name of Meypro A.G., Kreuzlingen, Switzerland). This solution is coated on a paper or film support and dried.

After exposure, the negative material is brought into contact with the positive material. Both are then exposed for up to 10 seconds to a temperature of 170 C. by means of a developer apparatus as described in French Patent 1,346,705 or by means of a glazing press or a drying drum. After separation of the two materials, a blue image on a yellow background is obtained.

The negative material prepared according to the above prescription has also still not changed after a relatively long storage time, whereas a material without compound 7 is unsuitable for use after relatively short storage.

What we claim is:

1. In a heat developable photographic material comprising a support bearing a light sensitive silver halide emulsion layer and containing a silver halide developing substance, the improvement according to which the material also carries a compound of the following general formula wherein R and R represent a member of the group consisting of hydrogen atoms, an alkyl and an aryl radical,

R represents agfiiiember of the group consisting of an aryl and a heterocyclic radical,

R and R together may represent the ring members forming a cyclohexyl ring, and

R represents a nitrile or nitro group.

2. A heat developable photographic material according to claim 1, wherein R is a nitro group.

3. A heat developable photographic material according to claim 1, wherein R is a. nitrile group.

4. A heat developable photographic material according to claim 1, wherein said component is a 1-aryl-2- nitroethanol.

5. A heat developable photographic material according to claim 1, wherein said compound is a l-phenyl-Z-cyanoethanol.

6. A process for producing photographic silver images which comprises exposing to a subject to be reproduced a photographic material as claimed in claim 1 and subjecting the exposed material to heat to develop a silver image therein.

7. A process of producing photographic transfer images which comprises exposing to a subject to be reproduced a photographic material as claimed in claim 1, subjecting the exposed material to heat While it is in contact with a non-light sensitive transfer material to develop a silver image in said exposed material, to transfer developer substance from the unexposed areas of said exposed materials to the transfer layer and to produce a visible image in said transfer material by the action of said transferred developer substance.

8 References Cited UNITED STATES PATENTS 11/ 1944 Baldsiefen 96-95 6/1962, Haist et a1. 9666 NORMAN G. TORCHIN, Primary Examiner.

J. T. BROWN, Assistant Examiner. 

1. IN A HEAT DEVELOPABLE PHOTOGRAPHIC MATERIAL COMPRISING A SUPPORT BEARING A LIGHT SENSITIVE SILVER HALIDE EMULSION LAYER AND CONTAINING A SILVER HALIDE DEVELOPING SUBSTANCE, THE IMPROVEMENT ACCORDING TO WHICH THE MATERIAL ALSO CARRIES A COMPOUND OF THE FOLLOWING GENERAL FORMULA
 7. A PROCESS OF PRODUCING PHOTOGRAPHIC TRANSFER IMAGES WHICH COMPRISES EXPOSING TO A SUBJECT TO BE REPRODUCED A PHOTOGRAPHIC MATERIAL AS CLAIMED IN CLAIM 1, SUBJECTING THE EXPOSED MATERIAL TO HEAT WHILE IT IS IN CONTACT WITH A NON-LIGHT SENSITIVE TRANSFER MATERIAL TO DEVELOP A SILVER IMAGE IN SAID EXPOSED MATERIAL, TO TRANSFER DEVELOPER SUBSTANCE FROM THE UNEXPOSED AREAS OF SAID EXPOSED MATERIALS TO THE TRANSFER LAYER AND TO PRODUCE A VISIBLE IMAGE IN SAID TRANSFER MATERIAL BY THE ACTION OF SAID TRANSFERRED DEVELOPER SUBSTANCE. 